Front system for a printed circuit board assembly having active-passive switching

ABSTRACT

The front system has an upper and a lower end piece (5) which are fastened to the upper and lower front corner region (3), respectively, of the printed circuit board assembly (3). An upper and/or a lower lever pull handle (19), which is fitted to the upper and/or lower end piece respectively, is used for levering the printed circuit board assembly into and out of the mounting rack. A latching mechanism (25) is provided to fix the lever pull handle in the appropriate position when the printed circuit board assembly has reached the point where it has been fully inserted into the mounting rack. A switching element (31) is integrated in the upper and/or lower end piece in such a manner that the switching element is actuated by the lever pull handle when it is in its fixed position. By this means, the printed circuit board assembly can be electrically enabled. The invention has the advantage that, as a result of its integration into the lower and/or upper end piece, the switching element can be moved to an accurately definable position. It is thus possible to permanently and reliably actuate the switching element with the lever pull handle even when an actuator of the switching element has only a small switching path.

This is a Continuation of International Application PCT/DE95/01080, withan international filing date of Aug. 16, 1995, the disclosure of whichis incorporated into this application by reference.

FIELD OF AND BACKGROUND OF THE INVENTION

The invention relates to new and useful improvements in a front systemfor a printed circuit board. More particularly, the invention relates toa front system having one or more lever pull handles for affixing thefront system to a mounting rack.

EP 0 304 772 B1 discloses a front plug system for a flat structuralcomponent (printed circuit board) having an end contact device. In thiscase, a front plug connector can be plugged onto a front element whichis located at the end of a printed circuit board assembly. This iscarried out by means of a pivot movement, in that the front plugconnector can be attached into a pivot bearing at one end of the frontelement. Located at the other end of the front element and front plugconnector is an end contact device which does not engage until after thefront plug connector is attached completely to the front element. Theengagement is achieved through operation of a closure device, which ispreferably provided by a screw that is likewise inserted into the otherend of the front plug connector, so that the operating contacts of theend contact device do not engage until the screw has been screwedcompletely into an oppositely located thread in the front element, andthe front element has thereby been attached completely. In this way, itis possible to ensure that the electrical signals which are passed viathe front element and the front plug connector are not released untilall the contacts between the front element and the front plug connectorhave been closed, this release of the electrical signals taking placesimultaneously. Conversely, it ensures that the front plug connector isrestricted before one of the contacts is interrupted when the front plugconnector is pivoted away.

Printed circuit board assemblies can be levered into and out of theplug-in slot in a mounting rack by means of insertion and withdrawalaids such as those known, e.g., from EP 0 194 515 B1. However, even inthe case of such printed circuit board assemblies that can be levered inand out, it is sometimes necessary to bring about organized releaseand/or interruption of the entire signal exchange, which proceeds viatheir rear plug connectors to a mounting rack motherboard and a data buslocated there. Thus, e.g., at the start of levering out a printedcircuit board assembly, it is desirable to bring about completeinterruption of the signal exchange to and from the printed circuitboard assembly without having to disconnect the contact between the plugconnector and the motherboard, even though other contacts are not yetdisconnected.

In order to solve this problem, the document Honeywell Outline, Sensorsand Automation, Year 9, Issue 1, pages 10, 12 proposes, in the article"Leiterplattenausbau ohne Systemunterbrechung mit Honeywell Schalternund Sensoren" Printed circuit board removal without system interruptionusing Honeywell switches and sensors! that, for example, a switch befitted to the edge of the printed circuit board, either on its top orbottom, and be connected to the main power supply, e.g. via appropriateconductor tracks. An interlocking mechanism, which fixes the printedcircuit board in its position in the mounting rack, acts on the switch.In the interlocked state, a bolt of the interlocking mechanism rests onthat edge of the printed circuit board to which the switch is fitted andcauses the switch to operate, and thus causes electrical activation ofthe printed circuit board. If, in contrast, the bolt is pivoted awayfrom the edge, then the switch is interrupted and the printed circuitboard is switched to be electrically inactive. An infrared component canalso be used instead of the switch.

OBJECTS OF THE INVENTION

A major problem with such devices is the fact that precise positioningof the switch on the edge of the printed circuit board isextraordinarily difficult. If, for example, the switch is soldered toappropriate conductor tracks on the printed circuit board surface, then,because of the soldering process, it is difficult to ensure that theswitching lever, particularly in the case of a miniature switch, can bepositioned sufficiently accurately that it is operated correctly whenthe bolt comes to rest on the edge of the printed circuit board.

One object of the invention, therefore, is providing a front system fora printed circuit board assembly equipped with electrical active-passiveswitching for the printed circuit board that is both precise anddurable. A further object of the invention is providing a front systemof elegant design that is both easy to operate and reliable.

SUMMARY OF THE INVENTION

These and other objects are achieved by the teaching of the independentclaims. Further advantageous embodiments of the invention are defined inthe dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and preferred embodiments thereof are explained in greaterdetail by means of the examples illustrated in the figures, in which:

FIG. 1 shows a perspective side view of a lower transverse rail of amounting rack and of a lower end piece, designed according to theinvention, for a front panel of a printed circuit board having a leverpull handle,

FIG. 2 shows a sectional view through the structure illustrated in FIG.1, with a snap-action switch provided as an integrated switchingelement,

FIG. 3 shows a sectional view through the structure illustrated in FIG.1, except that a Ball effect sensor and a magnet are provided as theintegrated switching element, and

FIG. 4 shows a sectional view through the structure illustrated in FIG.1, except that a light barrier is provided as the integrated switchingelement.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a perspective side view of the lower, front end region 1 ofa front system, designed according to the invention, for a printedcircuit board assembly 3. The printed circuit board assembly 3 is shownin FIG. 1 in the form of a representative lower, front corner regionthereof. The lower end region 1 in this case rests on the lowertransverse rail 37 of a mounting rack. The main components of the lower,front end region 1 of the front system are a lower lever pull handle 19,a lower end piece 5, and a front panel, which is not shown in FIG. 1.The lower end piece 5 has a central retaining function since it is used,on the one hand, as a support for the lever pull handle 19, which ismounted, in particular, via a hole 23 and an associated pin (not shown),such that it can rotate. On the other hand, the lower end piece 5 isalso used for holding the lower end of the front panel, which isadvantageously pushed into a groove 11 and is held via a screw thatengages with a hole 12. The connection between the lower end piece 5 andthe front, lower corner of the printed circuit board assembly ispreferably achieved by a retaining block 7 and by means of a screw whichengages a hole 8 therein.

Further components can be fitted onto the end piece 5. The end pieceillustrated in FIG. 1 thus includes a coding block 13, into which codingchambers 15 are incorporated for inserting coding pins. These codingpins can contact other coding chambers, which are positioned in anopposing relationship on the lower transverse support 37 and aresimilarly fitted with complementary-coded coding pins. In this way, itis possible to ensure that only a specific, selected printed circuitboard assembly can be positioned in a given plug-in slot in the mountingrack. Finally, there is also a guide pin 17 that is received by anopposing guide hole, thereby ensuring that the printed circuit boardassembly is inserted correctly, without tilting.

A lower lever pull handle 19, which can be operated by operating thehandle part 21, is used for levering the printed circuit board assembly3 into and out of the corresponding plug-in slot. While the printedcircuit board assembly 3 is being levered out, the handle must bepressed downwards so that at least one levering-out tab 27, projectingfrom the bottom of the handle, rests on an end edge 39 of the lowertransverse rail 37. Conversely, while the printed circuit board assemblyis being levered in, the handle must be pressed upwards so that at leastone levering-in edge 29, which likewise projects from the underside ofthe handle, can be supported in the interior of at least one engagementcutout 41. As evident from FIG. 1, the engagement cutouts 41 arelikewise located in the region of the end edge 39 of the lowertransverse rail 37.

Normally, there is also provided some mechanism on the end piece 5 bymeans of which the lever pull handle 19 is fixed in the appropriateposition, once the printed circuit board assembly 3 has reached thepoint at which it is inserted into the mounting rack completely. Forthis purpose, as illustrated in FIG. 1, the lever pull handle 19advantageously has a latching tab 25 on its upper surface. This latchingtab 25 is preferably mounted resiliently and is directed towards the endpiece 5 such that it projects upwards and engages behind a latching edge9 on the lower end piece 5. The latching edge 9, conversely, is directedtowards the lever pull handle 19 and points downwards so that it canclasp the latching tab 25.

Although not illustrated in FIG. 1, a corresponding arrangement,composed of an upper end piece with an upper lever pull handle mountedon it, such that it can rotate, is fitted in the same manner to thefront, upper corner region of the printed circuit board assembly 3. Thisupper lever pull handle engages in a corresponding upper transverse railof a mounting rack for levering the front system in and out.

According to the invention, a switching element is integrated into thelower and/or upper end piece in such a way that the switching element isactuated by its associated lever pull handle 19 when the handle reachesits latched position. In this way, the printed circuit board assemblycan be rendered electrically active, for example by activation of itspower supply. On the other hand, the printed circuit board assembly canbe switched to be electrically passive when the printed circuit boardassembly is levered out. More specifically, the printed circuit boardassembly is rendered electrically passive at the moment when the leverpull handle ceases to engage the integrated switching element. Thus, forexample, the release of the switching element by the lever pull handlecan cause the electrical power supply to the printed circuit boardassembly to be made passive.

By way of a first example, FIG. 1 shows a switching element 31 which isintegrated into the lower end piece 5. This switching element 31 ismounted in a retaining slot 10 which extends into the region of thelatching edge 9 of the end piece 5. A switching part (concealed and thusnot visible in FIG. 1) of the switching element, for example a switchinglever, projects into the region below the downwardly pointing latchingedge 9. Accordingly, the switching part is actuated when the lever pullhandle reaches the latched position, by the impact of its rear sideagainst the switching element. In the embodiment of FIG. 1, thisoperation is carried out by the end of the latching tab 25 that facesthe lower end piece 5. Preferably, the integrated switching element 31is electrically connected to the printed circuit board assembly 3 via acable connection or cable plug connection that is fitted to connectingcontacts 33 of the switching element 25. However, other types ofconnections are also possible. Therefore, the connecting contacts can,for example, be drawn down in the form of wires to the surface of theprinted circuit board assembly 3 and be soldered in holes presenttherein.

The active-passive switching according to the invention has theadvantage that the switching element 31 can be moved very exactly into aprecisely definable position as a result of its integration into thelower or upper end piece of the front system. It is therefore alsopossible to operate the switching element durably, reliably and withoutsignificant wear. This is especially the case if the switching means ofthe switching element has only a very limited range of movement forswitching. Furthermore, the switching is achieved by means of an alreadyexisting element, namely the lever pull handle. Finally, since theactive-passive switching function is completely integrated within theinventive front system, users of such front system are not subject toany restrictions at all regarding the positioning of components on theprinted circuit board assembly. In particular, no dimensionally accurateposition stipulations regarding electrical connections for the switchingelement are required.

The integrated switching element 31 is advantageously embodied as aso-called snap-action microswitch. The snap-action microswitch ispreferably actuated via a switching member provided on the lever pullhandle. FIG. 2 shows a design of this type by way of a sectionalillustration taken through the end region of the front system. Theswitching lever 55 of the integrated snap-action microswitch 51 in thiscase is operated by a switching member 50 which takes the form of a beadthat is situated on the rear side of the lever pull handle 19 facing theend piece 5. The switching lever 55 confronts the bead 50 of the leverpull handle 19 and is placed in a closed switch position when the leverpull handle 19 is in the fully latched position.

According to the invention, components based on other switchingprinciples can be integrated as switching elements in the end piece offront systems according to other embodiments. For instance, a Halleffect sensor can be used as the switching element. FIG. 3 shows anexample of this type, where a magnet 65 which is fitted onto or recessedinto the rear side of the lever pull handle 19 is used as the switchingmember. The Hall effect sensor 61 switches when the magnet 65, onreaching the fixed end position illustrated in FIG. 3, has approachedthe sensor 61 to a sufficient extent. The moment of switchingcorresponds to the moment when the printed circuit board assembly hasbeen inserted completely into the mounting rack.

Yet another design of the invention is illustrated in FIG. 4. Theintegrated switching element used there is a light barrier 71. Aswitching member 75, which is once again fitted to the rear side of thelever pull handle 19, breaches a light path of the light barrier 71 in ashading manner at the moment when the lever has reached its latchedposition. This is the case when the levering-in operation of the printedcircuit board assembly has been concluded and the latter has reached itsfinal, fully inserted position within the mounting rack.

The above description of the preferred embodiments has been given by wayof example. From the disclosure given, those skilled in the art will notonly understand the present invention and its attendant advantages, butwill also find apparent various changes and modifications to thestructures disclosed. For example, the positioning of the switchingmember can be varied, so long as the switching member can cause theintegrated switching element to switch between electrically active andpassive states in correspondence with the lever pull handle movingbetween fully latched and less than fully latched positions. Thus, whileit is preferable to provide the switching member on an upper portion ofthe rear surface of the lever pull handle near the latching tab, it isnot necessarily critical to do so. It is sought, therefore, to cover allsuch changes and modifications as fall within the spirit and scope ofthe invention, as defined by the appended claims, and equivalentsthereof.

What is claimed is:
 1. Apparatus, comprising:a) an end piece fastened toa front corner region of a printed circuit board assembly, said endpiece comprising a first latching element; b) a lever handle pivotablebetween a latched position and an unlatched position for levering theprinted circuit board assembly into and out of a mounting rack, saidlever handle comprising a second latching element; c) a switchingelement affixed to said end piece for selectively electricallyactivating and deactivating the printed circuit board assembly; and d) aswitching member provided on said lever handle;wherein: said firstlatching element engages said second latching element in the latchedposition; said first latching element fails to engage said secondlatching element in the unlatched position; and said switching member isdisposed in a position for switching said switching element from a firstswitching state to a second switching state when said lever handlepivots from the unlatched position to the latched position.
 2. Apparatusaccording to claim 1, wherein said switching element is integrated insaid end piece.
 3. Apparatus according to claim 1, wherein said endpiece has an orifice into which said switching element is affixed. 4.Apparatus according to claim 1, wherein said switching member comprisesa surface portion of said second latching element.
 5. Apparatusaccording to claim 1, wherein:said switching element comprises amicroswitch; and said switching member comprises a surface projection ofsaid lever handle.
 6. Apparatus according to claim 1, wherein:saidswitching element comprises a Hall effect sensor; and said switchingmember comprises a magnet.
 7. Apparatus according to claim 1,wherein:said switching element comprises a light barrier; and saidswitching member comprises an opaque element.
 8. Front panel system,comprising:a) a front element fastened to a printed circuit boardassembly, said front element comprising a first latching element; b) alever handle pivotable between a latched position and an unlatchedposition for levering the printed circuit board assembly into and out ofa mounting rack, said lever handle comprising a second latching element;c) a switching element affixed to said front element and arranged toactivate the printed circuit board assembly in a first switching stateand to deactivate the printed circuit board assembly in a secondswitching state;wherein: said first latching element engages said secondlatching element in the latched position; said first latching elementfails to engage said second latching element in the unlatched position;and said lever handle is disposed in a position for switching saidswitching element from the second switching state to the first switchingstate when said lever handle pivots from the unlatched position to thelatched position.
 9. Front panel system according to claim 8, whereinsaid front element has an orifice into which said switching element isaffixed.
 10. Front system, comprising:a) an upper and a lower end piecewhich are fitted to an upper and a lower front corner region,respectively, of a printed circuit board assembly; b) a lever pullhandle, which is fitted to one of said upper and said lower end piece,for levering the printed circuit board assembly into and out of amounting rack, said lever pull handle having means by which said leverpull handle is fixed in a latched position when the printed circuitboard assembly is in a fully inserted position in the mounting rack; andc) a switching element integrated in said one end piece such that saidswitching element is actuated by said lever pull handle when said leverpull handle is in the latched position.
 11. Front system according toclaim 10, wherein said one end piece has a retaining slot for receivingand mounting said integrated switching element.
 12. Front systemaccording to claim 10, wherein:said one end piece comprises a latchingedge; said lever pull handle comprises a latching tab; and in the fullyinserted position of the printed circuit board assembly in the mountingrack, said latching tab clasps behind said latching edge.
 13. Frontsystem according to claim 12, wherein said integrated switching elementis actuated by said latching tab of said lever pull handle.
 14. Frontsystem according to claim 10, wherein:said integrated switching elementcomprises connecting contacts.
 15. Front system according to claim 10,wherein said integrated switching element is a snap-action microswitch.16. Front system according to claim 15, wherein said snap-actionmicroswitch is actuated by a switch actuator contacting and actuated bysaid lever pull handle when said lever pull handle is in the latchedposition.
 17. Front system according to claim 10, wherein:saidintegrated switching element is a Hall effect sensor; a magnet is fittedto said lever pull handle to confront said Hall effect sensor when saidlever pull handle is in the latched position; and said magnet actuatessaid Hall effect sensor when said lever pull handle is in the latchedposition.
 18. Front system according to claim 10, wherein:saidintegrated switching element is a light barrier; a switching member isfitted to said lever pull handle to confront said light barrier whensaid lever pull handle is in the latched position; and said switchingmember actuates said light barrier by shading a light path of said lightbarrier when said lever pull handle is in the latched position.